Document falsification and product counterfeiting are significant problems that have been addressed in a variety of ways. One approach has been using latent or hidden images applied to or printed on articles to be protected. These latent or hidden images are generally not viewable without the assistance of specialized devices that render them visible.
One approach to the formation of a latent image is to optically encode the image so that, when applied to an object, the image can be viewed through the use of a corresponding decoding device. Such images may be used on virtually any form of printed document including legal documents, identification cards and papers, labels, currency, and stamps. They may also be applied to goods or packaging for goods subject to counterfeiting.
Articles to which an encoded image is applied may be authenticated by decoding the encoded image and comparing the decoded image to an expected authentication image. The authentication image may include information specific to the article being authenticated or information relating to a group of similar articles (e.g., products produced by a particular manufacturer or facility). Production and application of encoded images may be controlled so that they cannot easily be duplicated. Further, the encoded image may be configured so that tampering with the information on the document or label is readily apparent.
In existing systems, when an encoded image is decoded, the hidden content is revealed as a monochrome image. Alternatively, the hidden content is revealed as an image that has the exact same colors provided in each location of the printed artwork without the decoding device. While the hidden content may appear brighter or darker compared to the visible content, the image follows the colors present in the visible content. Using prior art methods, it is not possible to design the color appearance of the hidden content and to encode it in such way that there is no visual correlation between colors observable with naked eye in the visible content and colors in the decoded hidden content. What is needed is a process and method of encoding and decoding hidden images using two or more color components.